Arboriculture - Tree testament

A trio of recent reports on the benefits of urban trees set out to push the agenda with planners and councils, Jack Shamash explains.

Tree instatenemt in Bristol followed carriageway work as part of the city's strategy to require replacement planting - image: www.treebristol.com
Tree instatenemt in Bristol followed carriageway work as part of the city's strategy to require replacement planting - image: www.treebristol.com

At the end of June, three major reports came out showing how trees could play a role in improving life in cities. The publications were consciously released simultaneously to create a lasting impact on planners and local authorities.

The reports not only make a useful contribution to the debate about the future of Britain's trees. They also mark a wider recognition that trees are a vital amenity and should, wherever practical, be maintained as an integral part of the urban scene.

Anne Jaluzot, author of one report by the Trees & Design Action Group (TDAG), says: "We wanted to publish the reports together to make an impact. Each of the reports dealt with a slightly different subject, but they were all closely related."

London is the focus of the Green Benefits in Victoria Business Improvement District report, which attempts to estimate the value of trees in the area by quantifying their benefit to the community in both environmental and financial terms.

Canopy cover benefit

Perhaps the most important point that the report makes is that the biggest benefit is from large canopy trees. Until recently, insurers were putting local authorities under pressure to remove familiar landmarks such as oaks and London planes, often described as "forest trees" and seen as unsuitable for cities. The report puts the lie to this idea that big trees have no place in British towns.

A lot of hard numbers are put forward. There are 1,225 trees, which give the area 8.8 per cent canopy cover. Together with shrubs and other greenery, the trees remove 1.2 tonnes of pollutants each year, take in 18 tonnes of carbon and take on 112,400 tonnes of water that would otherwise run into storm drains.

The value of the trees - based on the calculation of the capital asset value for amenity trees - is around £27m per year. The appendix of the report gives details on how this value was compiled. Better parks and trees improve tourism, make London a better place to work, improve health and push up property values.

When it comes to trees, size is very important. Of the trees in Victoria, 29 per cent are London plane and the report suggests that it is vital to plant more of them. In recent years, most planting has been of smaller trees and if this trend continues the canopy cover will fall and central London will become a lot more uncomfortable. Without trees, the microclimate could rise by more than 5 degsC.

The report, which was compiled by a team of researchers, points out: "London planes provide more than twice the leaf area of all the other tree species combined." The big trees also prevent water runoff, which at times of heavy rain can overwhelm the Victorian drainage system.

The report concludes that there should be more planting and closer cooperation with private owners of trees - many of Victoria's trees are in private squares. It also suggests that local authorities should encourage Thames Water to recognise - and presumably subsidise - the contribution that the trees make.

Practical advice

The other two reports give practical advice on how this valuable asset should be managed. Jaluzot's Trees in the Townscape was funded by an assortment of local and regional authorities, private developers and non-governmental bodies as well as private nurseries such as Barcham Trees.

It was devised after extensive consultation with civil engineers, social landlords, planners and tree experts. Jaluzot explains: "We wanted to give an umbrella framework, to bring together advice on trees and help anyone working in this field."

The 83-page document is well laid out and written in the form of 12 principles that major landowners should follow. It offers a sort of step-by-step plan for anyone working in this area.

A great deal of emphasis is laid on planning. Professionals are encouraged to "know your tree resource", producing maps and plans that should be widely available. A tree strategy should also be drawn up. The report gives the example of Seattle, where the tree canopy had decreased from 40 to 18 per cent in just over 30 years. The city's strategy has the aim of increasing the canopy to 30 per cent by planting 650,000 new trees by 2037.

This tree strategy should be embedded into other aspects of planning and local government. Any new development should have rigorous requirements for planting and care of trees. There should be more tree preservation orders and conservation areas and local authorities should ensure that developers have to spend money if they pull down trees. In Bristol, for example, developers were forced to plant four trees for every one that they felled.

The importance of tree-friendly design is stressed. According to the report, there should be a "presumption in favour of large trees". In addition, utility companies should share conduits to minimise the amount of disruption caused by a repairs, it suggests. Local communities should take full advantage of trees to calm traffic or improve street appearance. Meanwhile, anyone involved in trees should constantly be stressing the benefit of trees in attracting birds and insects.

Much of the advice is fairly obvious. Buy goodquality trees and make sure that they are planted with sufficient room to grow and are given - or are able to obtain - the water they need. Jaluzot says: "This might all seem obvious, but when we spoke to many groups they had real problems because there was no system in place for maintenance. This has to be carefully thought out."

The report also has some very practical ideas. It suggests that "political, professional and community stakeholders should be created to champion the value of trees in the landscape". Local authorities should consider establishing a strategic tree forum of local organisations, park officials and residents. Volunteers could be used as tree wardens. In London's inner-city Hackney, this kind of scheme has reduced the failure rate of newly-planted street trees to one per cent.

Contractors working on utilities or street work should be required to show environmental awareness about trees. The report cites the case of the London Borough of Islington, which requires ISO 9001 accreditation for contractors working on its streets.

Rather like the Victoria report, the TDAG report suggests that trees should be carefully valued as an asset. It suggests that authorities should be risk aware rather than risk averse. Trees should be inspected and maintained regularly and potential risks should be monitored carefully.

It points out that fewer than one in three local authorities has a formal policy for managing trees in relation to liability for tree-related structural damage. It suggests that the London Tree Officers Association's risk limitation strategy should be generally adopted to ensure safety and reduce unnecessary felling.

Online toolkit

The third report, Neighbourhoods Green, is a partnership project primarily run by the Housing Federation. The online "toolkit" gives step-by-step advice for providers of social housing - local authorities, housing associations and the various arm's-length bodies set up for this purpose.

Project coordinator Nicola Wheeler says: 'Because of stock transfers, where housing has been transferred out of local authority hands, social housing providers are now responsible for an awful lot of trees but don't always have the skills to deal with them."

The toolkit aims to remedy this deficiency with a series of eight steps that housing providers should follow. These suggest the best ways of developing a tree strategy, which organisations to consult and what kind of judgements have to be made.

There is also a short but useful section on legal responsibility and the law and another covering how to manage risk. As with the other reports, this toolkit stresses the merit of knowing the value of the tree stock.

One section looks at the importance of involving residents. Simple jobs such as planting small trees, watering them or pruning can be done by community groups. Residents can be asked to "adopt" trees or become tree wardens and be directly involved in making decisions. This kind of activity not only increases local pride but cuts down on vandalism.

Many of the social homes will have their own private gardens. Trees in these areas have to be inspected and maintained. The report also has links to useful publications and websites.

Wheeler believes that the toolkit has struck the right balance. "We need a very proactive approach to ensure that the estates get benefit from trees," she points out. "We have to get as many residents as possible involved. After all, these trees are literally on their doorsteps."

The three reports

- Green Benefits in Victoria Business Improvement District

An analysis of the benefits of trees and other green assets in the Victoria business improvement district.

Sporsored by the Mayor of London, the London Climate Change Partnership and Treeconomics. www.victoriabid.co.uk

- Trees in the Townscape: A Guide for Decision Makers

Trees & Design Action Group.

www.tdag.org.uk

- Neighbourhoods Green

Tree management toolkit.

www.neighbourhoodsgreen.org.uk


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